Specification is ongoing in 3GPP for E-UTRAN (Evolved Universal Terrestrial Radio Access Network) that is the next generation of Radio Access Network. Another name used for E-UTRAN is the Long Term Evolution (LTE) Radio Access Network (RAN). A base station in this concept is called eNB (E-UTRAN eNodeB). The specifications also include the possibility to have an E-UTRAN base station to provide home or small area coverage for a limited number of users. This base station is called HeNB (Home eNodeB) in this document. The HeNB would provide normal coverage for the end users and would be connected to the mobile core network using some kind of IP based transmission. The coverage provided is called femto cell in this document. One of the main drivers of this new concept of providing Local Access is to provide cheaper call or transaction rates/charges when connected via the HeNB compared to when connected via the eNB. The HeNB would in most cases use the end users already existing broadband connection (e.g. xDSL, Cable) to achieve connectivity to the operators mobile core network and possibly to other eNB/HeNB. FIG. 1 illustrates an E-UTRAN with femto cells and HeNBs.
With the use of HeNBs the number of base stations the Core Network (CN) nodes need to interface with will be significantly higher than for a ‘normal macro deployment’, i.e. there may be 100 000's or even millions HeNBs in a network which will cause scalability problems in the CN nodes. This means that the MME (Mobility Management Entity) would need to have connections to all these HeNBs.
Therefore, it appears to be reasonable to include a ‘HeNB concentrator’ node in the network architecture, in the 3GPP specifications the concentrator node is referred to as a HeNB gateway (HeNB GW) or gateway node. It is also most likely that all the HeNBs will belong to a few TAs (Tracking Area) and that a one single TA is allocated for each HeNB. For example, FIG. 1 shows one scenario where “TA10” is allocated for all HeNBs. The location of a UE, user equipment, is known in CN on TA level or on a TA list level. This means that a new concept of multiple TAs for the registration and paging area has been introduced. Expressed differently, the TA list is a new concept that has been introduced to minimize the need for TA updates. The CN furthermore knows which eNBs serve a particular TA. So in case a UE terminated session needs to be established, the MME in a ‘normal’ macro deployment sends a page message to the macro eNB(s) serving the relevant TA(s).
However, in the HeNB case with a concentrator node, for example just one or a few TA(s) are exposed towards the CN (as a result of the concentration performed). So in this case, the TA does not uniquely pinpoint which HeNB the UE is camping on. For example, if 10 different TAs/TAIs are allocated and reused between all the HeNBs, then approximately 1/10 of the HeNBs belong to the same TA. If there exists 1 million of HeNBs in the network, then ˜100 000 of these would share the same TA/TAI. So a page message received from a MME would in the HeNB case mean that the ‘HeNB concentrator’ would need forward the page to all HeNBs that has been allocated the particular TA. This means that the ‘concentrator’ needs to spend a lot of processing power on sending the page message towards lots of HeNBs and a lot of load is generated on the backhaul transport network between the HeNB concentrator and the HeNBs. The backhaul is most likely owned by the subscribers where it is inappropriate to have the links flooded with useless paging messages on HeNBs where the UE being paged is not even allowed to access.
In the SAE/LTE 3GPP standards a concept known as CSG (Closed Subscriber Group) has been introduced. With CSG, particular HeNBs can be associated to certain UEs meaning that only these associated UEs are allowed to access the HeNB(s). The allowed CSGs are stored in the UE in a so called CSG Whitelist (or “Allowed CSG List”). Each HeNB broadcasts the CSG Identity allocated to it in System Information (SI) such that a UE that ‘hears’ (i.e. is able to read the SI) a CSG that is stored in its CSG Whitelist knows that it is allowed to access this HeNB. The association is also known by the CN (MME) which may perform an access control based on UE identity and the CSG identity of the current HeNB cell when an UE is accessing the network. This access control is mostly usable in the case when the stored CSG Whitelist in the UE is wrong. The CSG Identity can be, e.g., equal to the combination of TA Identifier and Cell Id but could also be considered to be a new identity.
Also in previous system architectures, sometime referred to as 3G systems, the concept of small area coverage base stations and the concept of CSG have been introduced. In a 3G system, such as WCDMA system, the Home eNodeB is referred to as a Home NodeB (without ‘e’) or HNB for short. Similarly, the HeNB concentrator or gateway node is referred to as a HNB GW, which is an abbreviation for Home NodeB gateway.
Therefore, there is a need for an improvement of the method for sending a page message to a mobile terminal in a telecommunication system.
In WO2007040452, there is disclosed a method for paging control to a femto radio base station of a radio access network. The paging is controlled by maintaining a paging control database of allowed user equipment units for which paging is permitted in a cell of a femto radio base station. When a page message is received, the paging control database is used to redefine an effective paging area for a target user equipment unit. Thus, with this method, the paging control database is accessed in order to determine which cells to page. Then, the page message is forwarded only to femto radio base stations which are included in the effective paging area.